A hidden toll: Australia’s cats kill almost 650 million reptiles a year



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A feral cat snapped by a remote camera in the wild.
NT government, Author provided

John Woinarski, Charles Darwin University; Brett Murphy, Charles Darwin University; Chris Dickman, University of Sydney; Sarah Legge, Australian National University, and Tim Doherty, Deakin University

Cats take a hefty toll on Australia’s reptiles – killing an estimated 649 million of them every year, including threatened species – according to our new research published in the journal Wildlife Research.

This follows the earlier discovery that cats take a similarly huge chunk out of Australian bird populations. As we reported last year, more than a million Australian birds are killed by cats every day. Since their introduction to Australia, cats have also driven many native mammal species extinct.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


We collated information from about 100 previous local studies of cats’ diets across Australia. These studies involved teasing apart the contents of more than 10,000 samples of faeces or stomachs from cats collected as part of management programs.

We tallied the number of reptiles found in these samples, and then scaled it up to Australia’s estimated cat population of between 2.1 million and 6.3 million. We also collated information from museums and wildlife shelters on the various animals that had been brought in after being killed or injured by cats.

We calculate that an average feral cat kills 225 reptiles per year, so the total feral cat population kills 596 million reptiles per year. This tally will vary significantly from year to year, because the cat population in inland Australia fluctuates widely between drought and rainy years.

On the hunt.
NT government, Author provided

We also estimated that the average pet cat kills 14 reptiles per year. That means that Australia’s 3.9 million pet cats kill 53 million reptiles in total each year. However, there is much less firm evidence to quantify the impact of pet cats, mainly because it is much more straightforward to catch and autopsy feral cats to see what they have been eating, compared with pet cats.

Binge eaters

According to our study, cats have been known to kill 258 different Australian reptiles (snakes, lizards and turtles – but not crocodiles!), including 11 threatened species.

The cat autopsies revealed that some cats binge on reptiles, with many cases of individual cats having killed and consumed more than 20 individual lizards within the previous 24 hours. One cat’s stomach was found to contain no less than 40 lizards.

Cat stomach contents, including several reptile parts.
Arid Recovery, Author provided

Such intensive predation probably puts severe pressure on local populations of some reptile species. There is now substantial evidence that cats are a primary cause of the ongoing decline of some threatened Australian reptile species, such as the Great Desert Skink.

By our estimate, the average Australian feral cat kills four times more lizards than the average free-roaming cat in the United States (which kills 59 individuals per year). But there are many more such cats in the US (between 30 million and 80 million), so the total toll on reptiles is likely similar.




Read more:
The war on feral cats will need many different weapons


The conservation of the Australian reptile fauna has been accorded lower public profile than that of many other groups. However, a recent international program has nearly completed an assessment of the conservation status of every one of Australia’s roughly 1,000 lizard and snake species.

Our research provides yet more evidence of the harm that cats are wreaking on Australia’s native wildlife. It underlines the need for more effective and strategic control of Australia’s feral cats, and for more responsible ownership of pet cats.

Pet cats that are allowed to roam will kill reptiles, birds and other small animals. Preventing pet cats from roaming will help the cats live longer and healthier lives – not to mention saving the lives of wildlife.


The ConversationThe authors acknowledge the contribution of Russell Palmer, Glenn Edwards, Alex Nankivell, John Read and Dani Stokeld to this research.

John Woinarski, Professor (conservation biology), Charles Darwin University; Brett Murphy, Senior Research Fellow, Charles Darwin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Sarah Legge, Associate Professor, Australian National University, and Tim Doherty, Research Fellow, Deakin University

This article was originally published on The Conversation. Read the original article.

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Australia’s reptiles may be spreading rat poison through the food chain



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Gould’s goanna is commonly eaten in Indigenous communities, but can contain high levels of rat poison.
Robert A. Davis, Author provided

Michael Lohr, Edith Cowan University and Robert Davis, Edith Cowan University

Introduced rats and mice have probably troubled most of us at some time in our lives. These pesky invasive rodents are found around the world. We usually target them with toxic baits to stop them spreading disease and causing environmental or commercial damage.

In some instances rat baits are useful. They can protect crops, reduce the spread of disease, keep the contents of your pantry from disappearing, or even protect endangered wildlife on islands where rats have invaded.

These baits are freely available to homeowners and are used liberally by pest controllers. However, they have potentially deadly consequences for native predatory animals that eat poisoned rats and mice.

Our new research shows that this secondary poisoning may be worsened in Australia by reptiles, which are extremely effective at spreading these poisons up the food chain – a process that may even have consequences for human health.




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Hidden housemates: rats in the ranks


While little is known about how well reptiles tolerate rodent baits, several studies have suggested that at least some reptiles are extremely resistant. In a toxicity study using one lizard species, all of the test subjects survived an incredibly high dose of the strongest poison on the market – over 4,000 times the poison per body weight needed to kill most rats.

This is probably good news for the lizards, but eating poison-supercharged reptiles may be a serious concern for their predators – and for us.

Humans eat lizards too

During a rat eradication program in the Montebello Islands, one goanna species was seen eating poisoned rats – without apparent ill effect – to the point that the green dye used in the bait was visible in their droppings. Unfortunately, this species of goanna is an important traditional food in Indigenous communities throughout Australia. To make matters worse, these poisons usually build up in commonly eaten parts of the goannas, like fat and liver tissue.

The risks associated with sublethal human exposure to rodent baits are not well known. However, recent studies in some wildlife species show that even mild chronic exposure to the longer-lasting poisons can lead to dangerous changes in the immune system.

With so many unknowns in a potentially dangerous situation, more research is urgently needed. We need to know how often and how severely the reptiles that humans eat are exposed to poison. Otherwise, some Indigenous people may have to choose between losing traditional hunting practices and risking exposure to rat poison.

Poison in the food web

In our research, we reviewed all published examples of wildlife deaths from exposure to rat bait. We found that rat poison has killed members of at least 32 native wildlife species in Australia. There are probably many more; only a few studies have looked at this problem in Australia, compared with other parts of the world.

We found that a small species of owl called the Southern Boobook is exposed to rat poison frequently, and sometimes lethally, in developed areas of Western Australia. Scavengers and prolific predators of rodents are likely to be even worse off – and these predators include a variety of threatened or endangered species such as Masked Owls, Tasmanian Devils and various species of quolls.

Most deaths will occur far from the original bait, as the poison travels through other species in the food web to reach its final destination. Without a better understanding of how baits affect Australian predators, we are unlikely to appreciate the scale of this invisible threat.




Read more:
Killing cats, rats and foxes is no silver bullet for saving wildlife


At present, powerful rat poisons are available at most supermarkets and hardware stores. The Australian Pesticides and Veterinary Medicines Authority is now reviewing how these are regulated because of concerns about human health and impacts on wildlife populations.

Other countries like the United States and Canada have already restricted the stronger poisons to licensed pest controllers. They have banned outdoor use and require lockable bait boxes to keep children and pets away from baits.

The ConversationThese steps might not be enough to overcome Australia’s unique risks, but allowing the current situation to continue is guaranteed to result in more poisonings of wildlife – and possibly unseen and unstudied effects on humans too.

Michael Lohr, PhD Student – Wildlife Ecology, Edith Cowan University and Robert Davis, Senior Lecturer in Vertebrate Biology, Edith Cowan University

This article was originally published on The Conversation. Read the original article.

Teaching reptiles to avoid cane toads earns top honour in PM’s science prizes


Michael Hopkin, The Conversation

A conservation biologist who is bidding to help Australia’s native animals learn to give cane toads a wide berth has been awarded the 2016 Prime Minister’s Prize for Science.

University of Sydney professor Rick Shine was given the award for his work in using evolutionary principles to boost the effectiveness of real-world conservation.

One example is his innovative use of “teacher toads” – small cane toads deployed in areas where native animals are threatened by the poisonous invaders. These small toads aren’t big enough to kill but are unpleasant enough to encourage animals such as quolls and lizards to steer clear of eating bigger cane toads in future.

Invading cane toads are spreading westwards across tropical Australia and have now reached the northern parts of Western Australia, growing bigger and faster as they go. By deliberately releasing smaller cane toads ahead of the invasion front, the project aims to give native animals a better chance of avoiding being caught on the hop.

Professor Shine’s research has also explored ways to stop cane toads reproducing, by lacing traps with pheromones from other species that attract cane toad tadpoles.

Originally a reptile biologist, Professor Shine began studying cane toads after one arrived at a site on the Adelaide River near Darwin, making him realise the significance of the threat the toads posed.

“The creatures like snakes and lizards that dominate our ecosystems, they’re the ones we have to focus on, they’re the ones we need to understand if we want to keep Australia’s ecosystems functioning,” he said.

Rick Shine on his love of reptiles.

UNSW Australia conservation ecologist Mike Letnic said that Professor Shine has been a role model for many scientists, particularly biologists tackling big questions about evolution and conservation.

“For me the biggest contribution he has made is in studying the rapid evolution of some species such as snakes, and obviously the work on cane toads feeds into that. The big challenge is whether you can harness that evolution for biological control,” he said.

“With cane toads it is not just the selection process but also the spatial sorting – faster, fitter toads are skewing selection by being at the invasion front.”

Cash and plastic

Other award recipients include Michael Aitken of the Capital Markets Cooperative Research Centre, who won the Prime Minister’s Prize for Innovation for his use of financial data to identify ways to improve Australia’s health markets.

Having initially developed ways to detect fraud in financial markets, Professor Aitken then turned his attention to spotting inefficiencies in health spending.

He and his colleagues have identified examples of “low-value treatments”, which are over-prescribed relative to the benefits they deliver – such as prostate screening and surgeries for chronic arthritis.

“We are looking at maybe A$20 billion per year that could be directed to improve health care in areas of genuine want,” he said. “These might be treatments that are of no great benefit. But surgeons are paid to do surgery – and if they don’t do surgery they don’t get paid, so they do it.”

Professor Aitken said you can learn a lot by studying the “low-hanging fruit” of health financial data to spot treatments that are being over-prescribed. But he then asks clinical experts to evaluate the evidence base for the treatments themselves.

Michael Aitken explains his data-driven approach.

Another scientist being honoured for innovation is Colin Hall of the University of South Australia, who has created a high-tech, all-plastic replacement for standard car wing mirrors.

His design is lighter and more sustainable than the conventional metal-and-glass design, but it had to pass a succession of stringent tests designed to mimic harsh motoring conditions before being adopted by the car industry.

“The hardest was the salt test – it had to be sprayed with very salty hot water for ten days,” Hall said.

Other tests included a thermal shock test in which the mirrors had to cycle rapidly between -40℃ and 80℃, 200 times in a row, to ensure they could handle temperature changes.

Colin Hall’s high-tech plastics have passed the test.
Prime Minister’s Prizes for Science/WildBear

Hall’s earlier research focused on designing high-tech plastics for spectacles. But while a pair of glasses might be replaced within a year, cars are designed to last at least a decade, which means the industry is very strict about which designs it approves.

Hall hopes that, in time, all of the metal components on cars can be replaced with plastic alternatives, thereby doing away with the highly polluting electroplating processes currently used in car production.

Peptides, proteins and ecosystems

Other prizewinners include Richard Payne of the University of Sydney, whose work on re-engineering protein molecules found in nature promises to give us new ways to treat stroke, malaria, tuberculosis and even cancer, and has earned him the Malcolm McIntosh Prize for Physical Scientist of the Year.

University of Queensland conservation scientist Kerrie Wilson has won the Frank Fenner Prize for Life Scientist of the Year, for her work on evaluating “ecosystem services” – the benefits provided by natural resources such as clean air, water and food.

Perth teacher and former geoscientist Suzy Urbaniak has won the prize for excellence in secondary school science teaching, while the award for primary school science education went to Sydney-based Gary Tilley.

The winners, who will share a prize pool of A$750,000, will receive their prizes from Prime Minister Malcolm Turnbull and Science Minister Greg Hunt at a dinner in Parliament House this evening.

The Conversation

Michael Hopkin, Environment + Energy Editor, The Conversation

This article was originally published on The Conversation. Read the original article.